NutLoose was just trying to be helpful but two of the links he posted were for the patch for the J Cutter that replaced the curved blade knife the O.P. was asking about. The Americans used a J Cutter at the time and I guess that’s why it was copied by the R.A.F.
The curved knife was for cutting shroud lines and puncturing dinghies not for survival in a hostile environment!
Try looking for a pre-90’s flying coverall from one of the many second hand sellers (including eBay) and cutting off the patch.